The field of the invention is paperboard die cutting, and the invention relates more particularly to the continuous waste removal from a previously die cut web of paper or paperboard.
A plurality of fixed pins are threaded into a rotary cylinder, and the pins penetrate waste material in a continuous web of paper or paperboard which is supported by an anvil roller. Thus, as a particular piece of waste from the web approaches the nib between the anvil roll and the rotary cylinder which supports the stripper pins, a stripper pin penetrates the waste which, in turn, is supported by the anvil roller and passes through the piece of waste and into a recess in the anvil roll which is usually a groove in the anvil roll. The pin, as it continues around the rotary pin cylinder, carries the piece of waste material until an ejection sleeve contacts an internal roller within the rotary pin cylinder, which internal roller forces the ejection sleeve outwardly, pushing the waste piece from the ejection pin and into a waste removal chute. As the pin continues around the rotary pin cylinder, the ejection sleeve is permitted to retract so that another piece of waste can be removed.
Other waste removal methods include a vacuum system wherein the die cut web passes over the mouth of a vacuum tunnel which draws the waste from the web. This system, however, requires essentially perfect die cutting so that the waste material will readily be drawn from the web. In practice, this requires rather frequent sharpening of the die cutting system so that the pieces are readily removed by vacuum. Furthermore, this system is quite ineffective for very small pieces of waste and likewise will not operate at a very high press speed.
For some continuous cutting systems, the waste can be contained in a continuous spool in which case the waste is simply rewound onto a spool. This system requires, however, that there be no internal pieces to be removed which are not connected to the waste web. This system also requires periodic shutdown to remove a full spool of waste web.
Another waste removal system also includes stripper pins, but rather than using ejection sleeves, a plurality of fixed combs are placed along the surface of the cylinder to comb the waste parts from the stripper pins. One difficulty with this system is the tendency of the combs to be compacted with fibers often leading to the breaking of the stripper pins. It is also an expensive system to set up and maintain.
For most high speed applications then, the use of the stripper pins in combination with ejection sleeves is most desirable. A major disadvantage with such system, however, occurs when the web repeat length is changed. This, in the past, has required a complete change of rotary pin cylinder and its internal eccentric cam sleeve which results in a substantial changeover cost every time the web repeat length is changed.